Delay powder



Patented Aug. 16,1949

UNHTED TES P I @FFHQE No Drawing. Application November 30, 1945, SerialNo. 632,101

(Granted under the act of March 3, 1883, as amended April 30, 1928; 3700. G. 757) Claims.

The invention described herein may be manufactured and used, by or forthe Government for governmental purposes without the payment to us ofany royalty thereon.

This invention relates to delay powders for use in fuzes of varioustypes, the powders being an improvement on the type of powder disclosedin Patent No. 1,877,127, dated September 13, 1932.

In the patent cited, delay powders were described comprising a metallicchromate, a metal adapted. to react with oxygen to form a solid, and abinder, Such powders have found extensive use for various purposes,particularly in closed systems where the development of gaseous productsof combustion by a delay powder would be objectionable if not definitelyprohibitive. OW- ing to the special property of such powders to producelittle or no gas upon combustion, new demands have arisen in connectionwith their application, such demands making necessary powders having amuch slower rate of burning than is obtainable with the type formerlydeveloped. The reason that the chromate-metal powders cannot be adjustedby altering the proportion of the ingredients to obtain sufiicientlyslow burning delay trains, resides in the fact that slow burning powdersof that type are very difficult to ignite and when used in delay trainsof small diameter they often fail to burn completely through the delaytrain. The small quantity of powder in the delay train does not evolvesufficient heat to allow radiation to the metal of the fuze and stillprovide sufficient heat to maintain combustion. A further difilculty isthat while the powders are essentially gasless, the use of linseed oilor other organic compound as a binding agent results in the developmentof a small but definite amount of gaseous products. In closed systemseven small amounts of gaseous products decrease the uniformity ofburning, this being accentuated with the slower burning powders.

The present invention has as its primary object the production of agasless delay powder designed to overcome the deficiencies mentionedabove. The objectives desired have been accomplished by combiningreactions between solid oxidizing agents and metals with an entirelydifferent type of reaction, viz., that between finely divided metals andsolid non-metallic elements,

such as sulphur, red phosphorus, selenium. and tellurium. It has longbeen known that when many metals in finely divided state ar mixed withsulphur such mixtures are readily ignitable and in many cases burn toyield only solid prod- 55 ucts, i. e., sulphides of the metal. We foundby experiment that by formulating delay powders so that a reactionbetween certain solid oxidizing agents and metals was involved and atthe same time a reaction occurred between the particular metal used anda solid non-metallic element, the ignitability of such composition wasmuch improved over that of a composition containing only these solidoxidizing agents and a metal. It was found further that the reactionproducts were entirely solid and practically no fumes fromvolatilization occurred even at the high temperatures produced by theburning composition, if metals having relatively high melting pointswere used, e. g., inon, titanium, manganese, chromium, aluminum, etc.

The solid oxidizing agents employed are such that when they react withthe metals in the presence of solid non-metallic elements, the reactionproducts are entirely solid and practically no fumes or gaseous productsoccur even at the high temperatures produced by the burning composition.The compositions formulated according to the present invention are as aconsequence substantially fre of materials which form gaseous productsof combustion when the mixture brurns. Examples of oxidizing agents thatmay be used in practicing the invention are: oxides of heavy metals, e.g., ferric oxide, magnetic iron oxide, cuprous oXide, cupric oxide,silver oxide, lead oxide, lead peroxide, and red lead; and alkalineearth metal peroxides, e. g., barium, calcium and strontium peroxides.

Examples of compositions which have been especially successful inproviding slow burning, readily ignitable, gasless delay powder trainsare as follows:

No. 1: Per cent Silver oxide 50 Iron Phosphorus 25 Cuprous oxide 80Manganese 10 Phosphorus 10 Ferric oxide (Fezos) Manganese 45 Sulphur 10Barium peroxide Chromium 25 Sulphur 15 The burning time of a powdercolumn 2" long 3 V and .22 in diameter for each of the examples givenabove is as follows:

Seconds No.1 -n 6 No.2 12 No.3 9 No. 4

,a metal, and compositions composed of a solid oxidizing agent and asolid non-metallic element,

when adjusted to burn very slowly, are difficult to ignite and whenignited have a tendency to cease burning in delay trains of smalldiameter; on

the other hand compositions involving the reactions between the finelydivided metals and solid non-metallic elements are readily ignitable butburn entirely too fast for use as slow burning delay'powders. Bycombining these reactions, the objections to each separate reaction areovercome, and delay powders of improved characteristics over thosepreviously disclosed are obtained, i. e., slow burning compositionsresult which readily ignite and when the compositions are loaded incolumns of small diameter burn completely through the columns. This isindicated by the data in the examples but additional test data show thatwith delay trains of smaller diameters, still slower burning of thepowders is obtained, due to reduction in amount of heat liberated, untildelays of the order of 20 seconds per inch of powder train ispracticable without ignition failures or failures to burn through whenonce ignited. v

Such slow burning is unusual and this characteristic of the new delaytrains is of much significance since it permits longer delays incompletely obturated fuzes than hasbeen attained heretofore.

The new powders are relatively simple to prepare provided close controlis exercised over the granulation of the ingredients. It is desirablethat the solid oxidizing agents and the metal be sufliciently fine thatthey will pass a 250 mesh screen. The powders may be mixed'in the drystate, or wet with water, carbon tetrachloride or other liquid to reducethe possibility of accidental ignition in manufacture. After thoroughmim'ng the powders are granulated by passing through screens ortreatment in mechanical granulators commercially obtainable for suchpurposes. No binding agent to. assist in granulating has been foundnecessary although such might be used if necessary in some special case.

Powders of this type have been found to be non-hygroscopic and ofexcellent stability. They are entirely non-explosive since they evolveno gas upon combustion.

We claim:

1. A substantially gasless powder comprising a mixture of a finelydivided solid non-metallic element selected from the group consisting ofsulphur, phosphorus, selenium and tellurium, a finely divided heavymetal'oxide, and a finely divided metal which reacts with saidnon-metallic element and said heavy metal oxide upon ignition, saidnon-metallic element, heavy metal oxide and metal being so proportionedthat when the mixturethereof is ignited and burns no substantialquantity of gaseous products will be evolved and the said powder beingsubstantially free of materials which form gaseous products ofcombustion when it burns.

2. A substantially gasless power comprising a mixture of a finelydivided solid non-metallic element selected from the group consisting ofsulphur, phosphorus, selenium and tellurium, finely divided silveroxide, and a finely divided metal which reacts with said non-metallicelement and said silver oxide upon ignition, said non-metallic element,silver oxide and metal being so proportioned that when the mixturethereof is ignited and burns no substantial quantity of gaseous productswill be evolved and the said powder being substantially free ofmaterials which form gaseous products of combustion when it burns.

3. A substantially gasless powder consisting essentially of a mixture ofabout 50 parts of finely divided silver oxide, about 25 parts of finelydivided iron, andabout 25 parts of finely divided phosphorus.

4. A substantially gasless powder comprising.

a mixture of a finely divided solid non-metallic element selected fromthe group consisting of sulphur, phosphorus, selenium and tellurium,finely divided ferric oxide, and a finely divided metal which reactswith said non-metallic element and said ferric oxide upon ignition, saidnon-metallic element, ferric oxide and metal being so proportioned thatwhen the mixture thereof is ignited no substantial quantity of gaseousproducts will be evolved and the said powder being substantially free ofmaterials which form gaseous products of combustion when it burns.

5. A substantially gasless powder consisting essentially of a mixture ofabout 45 parts of finely divided ferric oxide, about 45 parts of finelydivided manganese, and about 10 parts of finely divided sulphur.

' GEORGE C. HALE.

DAVID HART.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATEN'IS Number Name Date 1,877,127 Hale Sept. 13, 19321,971,502 Piccard Aug. 28, 1934 2,395,045 Graft Feb. 19, 1946 2,416,639Pearsall Feb. 25, 1947 FOREIGN PATENTS 7 Number Country Date 3,923 GreatBritain 1881 24,377 Great Britain 1899 385,834 Great Britain Jan. 5,1933

